Data signals may be distorted when transmitted over a high speed serial data link. The amplitude and phase distortion of the data signal generally depend on the channel characteristics of the serial data link through which the data signal is transmitted. As the channel length increases and/or the frequency of the data signal increases, channel loss may become significant. The channel typically has a low pass filter characteristic that may distort the high frequency components of the transmitted data signal. This may reduce the eye opening pattern at the receiver and increase inter-symbol interference (ISI).
Present techniques for channel equalization of a high speed serial data link may include the use of a finite impulse response filter at the transmitter to attenuate low frequency components of the data signal with respect to high frequency components. At the receiving end of the channel, a flatter frequency response may be achieved. Additionally, a decision feedback equalizer (DFE) may be employed at the receiver to cancel ISI from one or more previously transmitted data bits. However, these techniques generally do not provide sufficient attenuation for frequency components below 1/10 of the Nyquist frequency, which results in higher residual ISI when transmitting long strings of 1s or 0s over the serial link. The higher residual ISI reduces the voltage margins and makes the detection of a subsequent 0 (after series of 1s) or a subsequent 1 (after 0s) more difficult.